Effectsofheatstressonvisualattentionnetwork:afunctionalMRIstudy

Objective Toinvestigatetheeffectofpassivehyperthermiaonattentionnetwork withtheevent-relatedfunctionalmagneticresonanceimaging (fMRI). Methods Thirtyparticipants wererandomlydividedinto2groups (hyperthermiagroupandcontrolgroup).Theyperformedthe attentionnetworktest (ANT) withevent-relatedfMRIinahot (50℃and40%relativehumidity) or neutral (20℃and40%relativehumidity) environment,respectively.Thenetworkscoreswere analyzedusingamultivariateanalysis (MANOVA) withintheGLMpackage,withgroupasthefixed factor.Univariatepost-hoctestswithTukeycorrectionsformultiplecomparisonswereusedto investigategroupdifferencesoneachofthethreenetworks.ThefMRIdatawererealigned,normalizedandthensmoothedwith6mmFWHMkernel.ThefMRIresultsofthethreeattention networkswerecomparedbetweenthehyperthermiaandthecontrolgroupsusingatwo-samplet-test respectivelywithSPM8.Thestatisticalmapsweregeneratedwithanintegratedthresholdata correctedlevelofP<0.05. Results Thebehavioralresultsshowedthatheatstressenlargedthe scoresoftheexecutivenetwork[ (82.56±20.89) msvs (58.55±8.96) ms,F=16.683,P 0.05).ThefMRIresultsshowed that: (i) heatstressenhancedtheactivityintherightsuperiorfrontalgyrus (voxelnumber=39,t= 3.02,P<0.01) anddepressedtheactivityintherightmiddleoccipitalgyrus,leftinferiorparietal lobuleandleftculmen (voxelnumber=49,86,97;t=-2.86,-3.69,-2.72;andP<0.01,respectively) inthealertingnetwork,(ii) heatstressenhancedtheactivityinthetemporallobe (voxel number=29,58;t=5.00,4.57;andP<0.01,respectively) anddepressedtheactivityinthefrontal lobe,parietallobeandoccipitallobe (voxelnumber=29—85;t=-5.4—-2.61;andP<0.01,respectively) intheorientingnetwork,and (iii) heatstressenhancedtheactivityinthedorsolateral prefrontalcortex (voxelnumber=35,58;t=2.99,3.10;andP<0.01fortheleftorright dorsolateralprefrontalcortex,respectively) butnotaffectedtheactivityintheanteriorcingulate. Conclusions Heatstressimpairedtheexecutivefunction,especiallytheefficiencyofresolving conflict.Thenegativeeffectsofheatstressonalertingandorientingwereovercomebyvariantregional brainactivation. Key words: Heat; Attention; Magneticresonanceimaging